Harbor Freight compressor that won't inflate a bike tire?

by Bob
(Corpus Christi, TX)

Harbor Freight (Central Pneumatic) air compressor

Harbor Freight (Central Pneumatic) air compressor

Have a 90 psi Harbor Freight compressor. Pressure guage reads 90 psi when it shuts off, but still can barely inflate bike tire to 45 psi. Tried on car tire and takes forever to build up from 29 to 32 psi. This just happened since using a week ago.


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Bill says....

Bob, which is showing the 90 PSI, the tank gauge or the regulator gauge?

Better question, what is the tank gauge and the regulator showing?

Thanks,

Bill

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Jul 27, 2011
COMPRESSOR GUAGES
by: BOB

I have 2 guages on either side of regulator. The tank doesn't have a guage. When I decrease pressure using regulator, only one guage changes.

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Bob, I think the other gauge is the one that shows the air pressure in the tank. What is the pressure showing on both, please?



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shane/ builds up 50 pounds of pressuer then belt squillls

by shane
(palatka, florida)

hi i y old compressor just blew up so i bought a new harbor freight compressor pup and instaled it on y old tank and electric 5 hp...i took the check valve out but y proble is the copressor builds up 45 psi and then the belt starts to smoke. i tried to turn the will by hand but their is alot of pressuer....please help

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Bill says...

Shane, the belt is smoking because the pump sheave sounds like it's starting to lug after the 45 PSI is reached.

Something is affecting the ability of the pump to reciprocate, and that's slowing the sheave, and the belt slips in it and starts to smoke.

I don't know the why of you taking out the check valve, as it is necessary under normal compressor operations. Please have a look at Check Valve linked from the Valve page, for details of it's operation.

If the pump is sized right for a 5 HP electric motor, and it's new and properly installed, then I'm thinking a back pressure issue.

Pull the line from the pump to the tank and see if the pump/motor runs OK with no load. If it does, then I would like to try to add a load.

You could put a needle valve in that line, with the tank end open to atmosphere through the needle valve, and then close the needle valve slowly while running the pump. If you can emulate the slowing pump with the needle valve still open but with flow restricted, then you know, it's a back pressure problem causing the pump to lug.

Why though? A 5HP motor should have tons of power to pump up to the normal cut out pressure point.

If the pump is running correctly, then it's something you have done on the install. Based on the information you provided, I can't pinpoint what.

Good luck.

Bill

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compressor will not build pressure

by harry
(marietta, ga.)

Harbor Freight Model 67847

Harbor Freight Model 67847

Harbor Freight Model(67847) 2.5, 21 gal. (Not building pressure)

Symptoms: Seized motor, would not start.

The reset switch would Trip each time i turn compressor on.

I disassemble the pump, and noticed it was the piston which was "seized", which explained why the motor would not turn, causing the Reset switch to trip.

I "knocked" the piston back into position, reassembled pump and the motor started up.

However, I noticed no pressure indicated on the gauges.

I disconnected the tubing: from the pump to the tank; and I can "feel" air coming out of the pump. I can put my finger on the tubing while it is running. I am not sure if it this pressure is strong enough going into the tank.

I "sprayed" liquid over all the fittings for the pump to make sure there are no leaks from my inspection. (no air bubbles)

I can "feel" air blowing out of the "oil cap" when the compressor is on. I don't know if this is normal.

is replacing the entire pump mechanism my solution?
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In disassembling the pump and "knocking" the piston back into alignment, I suspect you - or the original failure - dislodged or damaged the piston seals, and air is blowing by them into the oil sump and out the oil fill vent.

Compressed air will always travel to the point of least resistance, meaning that if it's easier for the air to bypass seals than to be driven into the tank against increasing pressure, then that is what it will do, and you will not get any pressure buildup in the tank.

Given that this compressor was on sale for $139 when it was new, and not knowing how much you will pay for parts if you can find them, or how much "fun" you have doing work like this yourself, all I can ask is there sufficient fun in doing it yourself rather than replacing the air compressor and keeping the working parts from the old as spares? Your call.

Cheers,

Bill







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B3800 pumps up to 40 psi stays running but wont ...

by lee
(jones)

its a B3800 pump i tnk its a 80 gal comp have no idea whats wrong dosent make any funny noise runs at correct speed just wont pump up

B3800pumps up to 40 psi stays running but wont pump up any more
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Lee, not much to go on here. Please see the troubleshooting section on the site map page, read the page about why air compressors won't build pressure, do the checks, and post a comment here with what you found.

Cheers,

Bill

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